In a metal-air battery, oxygen in the atmosphere is used as a positive-electrode active material to perform redox reaction of this oxygen at an air electrode that is a positive electrode. On the other hand, redox reaction of metal is performed at a metal electrode that is a negative electrode. The metal-air battery has a high energy density, thus being expected as a role such as an emergency power supply at the time of disaster or the like.
The air electrodes are disposed, for example, on both sides of a housing, and the metal electrode is opposed to the air electrodes via an electrolyte (see FIG. 1 in JP-A-2015-99740). In the metal-air battery described in JP-A-2015-99740, the metal electrode is configured of a current collector and electrode active materials formed on both sides of the current collector.